Most agricultural row-crop planters, such as, for example, the John Deere 7000 series planter 10, of which FIG. 1 is a representation, comprises of a plurality of individual row units 14 spaced along the length of a transverse tool bar 12. Each row unit includes a subframe 16 which supports a seed hopper 20 containing a supply of seeds to be planted. Disposed below the seed hopper 20 is a seed meter with a seed belt housing 30 which dispenses individual seeds 32 at regular spaced intervals into a seed tube 36. The seed tube comprises a rearwardly curving forward and rearward wall members and opposing sidewall members thereby defining a rearwardly curving passageway. The seeds discharged from the seed meter 30 are received into the open top end of the seed tube 36 and are guided rearwardly by the rearwardly curving passageway until being released into the seed furrow 38 upon exiting the open bottom end of the seed tube 36 disposed a short distance above and substantially in line with the seed furrow 38. The furrow opening assembly 24 forms the seed furrow 38 forwardly of the seed tube. The furrow closing assembly 26 covers the deposited seeds in the furrow 38 with soil.
Disposed at approximately the midpoint of the seed tube 36 is a seed sensor 40. U.S. Pat. No. 5,533,548 to Bergland et al., hereby incorporated by reference, discloses a seed tube with a seed sensor mounted thereto. FIG. 2 illustrates an enlarged detailed view of the seed tube 36 with the seed sensor 40 mounted thereto illustrated in FIG. 1, but with the seed tube in cross-section, and showing the “ramp” in the seed tube as disclosed in Bergland '548. The purpose of the seed sensor 40 is to detect seeds as they pass through the seed tube as part of system for determining a seed population count. The seed sensor also operates as part of a warning system to notify the planter operator by an audible and/or visual alarm if the sensor fails to detect any passing seeds over a predefined period of time, which would indicate a problem with the row unit, such as the seed hopper running empty, or a malfunction of the seed meter, or the sensor, etc.
There are various types of sensors suitable for detecting seeds passing through a seed tube. Photoelectric sensors, such as the type manufactured by Dickey-John Corporation of Auburn, Ill., are among the most common sensors used with seed tubes. Continuing to refer to FIG. 2, photoelectric seed tube sensors generally include a light source element 40A and a light receiving element 40B disposed over apertures 42, 44 in the forward and rearward walls of the seed tube. Whenever a seed passes between the light source and the light receiver, the seed interrupts the light beam and the seed is detected.
It has been found that, the aperture 44 and/or the seed sensor element 40A may act as catch points for seeds traveling through the seed tube, thereby causing the seeds to ricochet off the catch point. Additionally, due to differences in fabrication tolerances of the wall thicknesses of the seed tubes and in dimensional tolerances of the sensor elements, and due to improper installation and other factors, the sensor element 40A may project into the seed tube instead of being flush with the interior surface of the seed tube wall as intended, thereby also presenting the problem of interference with the trajectory of the seed passing through the seed tube.
It is well recognized that proper and uniform spacing of seed in the furrow is essential to maximizing crop yield. Thus, any interference with a seed passing through the seed tube will result in inconsistent seed spacing in the furrow, whether due to some seeds passing more quickly through the seed tube than others, or as a result of the seed trajectory being effected upon exit of the seed from the seed tube. Various designs have been proposed to address the problem of minimizing catch points in the seed tube which interfere with the trajectory of the passing seeds.
For example, Bergland '548 (FIG. 2) proposes thickening the forward wall 46 above the sensor aperture 44 thereby forming an inwardly projecting ramp 48 above the sensor 40A. The ramp 48 purportedly serves as a transition to smoothly direct the seeds inwardly and away from the sensor element 40A projecting into the tube passageway through the aperture 44. Despite the purported function of the ramp to direct seeds inward and away from the seed sensor catch point, tests on commercial embodiments of the Bergland' 548 apparatus show that a catch-point is still present at the bottom of the aperture and/or at the bottom of the sensor element 40A for seeds traveling through the seed tube along the path of travel indicated by reference number 50, resulting in seeds bounces or ricocheting wildly off the seed sensor element 40A.
Another attempt to resolve the problem of catch-points in the seed tube is illustrated in FIG. 3, which is intended to represent the proposed solution disclosed in U.S. Pat. No. 6,332,413 to Stufflebeanm et al. In Stufflebeanm '413, the lower portion of the forward wall 46 of the seed tube below the sensor aperture 44 is stepped forward of the upper portion of the forward wall 46 above the sensor aperture 44. Although, the offset or stepped lower wall structure proposed in Stufflebeanm '413 appears to resolve the catch-point problem within the seed tube, providing such a large step or offset to avoid the catch-point presents additional problems.
First, in many applications, providing an offset sufficient to avoid catch-points is not possible due to space restrictions.
Second, a large offset negatively effects the ideal trajectory of the seed as it passes through the seed tube. Ideally, seeds will consistently contact the forward wall just above the aperture 44 and then slide along the rearwardly curving forward wall until exiting the tube. The larger the offset, the longer the seed will be in free-flight after passing the aperture before it again contacts the front wall, resulting in increased velocity of the seeds, which in turn results in greater force on impact when the seeds contact the forward wall again. Furthermore, the farther down the tube the seeds contact the wall, the greater the curvature and thus the closer the angle of incidence of the seed to being normal or perpendicular to the wall at the point of impact. The greater velocity, combined with the more perpendicular angle of incidents, results in greater likelihood of seed ricochet and inconsistent velocities and trajectories of the seeds upon exiting the seed tube.
Accordingly, there remains a need in the industry for a seed tube which not only eliminates catch-points in the seed tube resulting from the sensor apertures and sensor, but which minimizes any disturbance in the ideal trajectory of the seed passing through the seed tube.